Scientific studies have proven that a higher skin temperature in bed has a positive effect on the sleep of a person sleeping said bed. Scientific research has shown that warming the bed to get a small increase in skin temperature results in falling asleep faster, less awakenings during the night, longer sleeping time and more deep sleep.
Many people suffer from bad sleep. A survey in the USA in 2008 revealed that 65% of the adults experience bad sleep, stating that they have more than 2 nights a week not sleeping well. When these persons were asked for the reasons, they mentioned among other reasons that they have cold feet and/or feel either too warm or too cold during night.
Electrical blankets for raising the temperature in bed are well known and already exist for decades. However, the major disadvantage of conventional electric blankets is the fact that their temperature is not controlled. A constant power input is applied, and for some blankets the power setting can be changed in a few discrete steps. However, such a change of power setting does not take into account other conditions such as, for example, the presence of additional blankets on top of the bed, different metabolism of users in the bed or the room temperature. Thus, users of electric blankets often complain that the bed was heated too much during the night.
U.S. Pat. No. 4,433,062 describes a system that can detect the presence of a human body in the bed by a human body detection means for detecting retiring or rising of a user. The human body detection means is either pressure sensitive, or it may be a system using temperature signals in accordance with the presence or absence of a living human body. The preset temperature is automatically raised when the user rises so that the user is allowed to fall asleep again. The higher temperature preset is automatically decreased when the user goes to bed, and the presence of the user's body in the bed is detected.
US patent application publication US 2009/0099631 A1 discloses a multi-zone electric heating blanket which may be shaped to cover the outstretched arms or other body parts of a patient. The blanket includes two body part portions and a connecting bridge. A power controller may supply power to heating elements in both body part portions based on a temperature sensor in one of the body part portions. The temperature sensor is positioned such that it is always in direct contact with the patient's skin. The blanket comprises two temperatures sensors at maximum, and the temperature regulation is to prevent overheating.
Furthermore, in electric blankets, heat is supplied uniformly to the whole bed instead of being supplied to those areas only which in fact require heating. Blankets having a separate heating zone for the feet of a sleeping person exist, but again have a fixed heating power only rather than a temperature control.
There is a need for a bedding layer for improving a person's sleep, which bedding layer provides a better adjustment of the temperature within a bed.
More specifically, it is desirable to tune the temperature control of individual zones of the bedding separately accounting to the fact of whether a part of the sleeping person's body is lying on top or underneath an individual heating zone Therefore, it would be advantageous to detect the position of a body lying on a bed, without the need for direct contact between sensor and body. A solution could be to use pressure sensing mats that are commercially available. Such a pressure sensitive mat is placed underneath the body of a lying person, and the mat is capable of detecting a two-dimensional pressure distribution.
However, such mats are expensive, and not comfortable to lie as they are made of plastic-like material having limited flexibility and no moisture transmission.